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Re: [Qemu-devel] Support for multiboot images in elf64 (EM_X86_64) forma
From: |
Paul Brook |
Subject: |
Re: [Qemu-devel] Support for multiboot images in elf64 (EM_X86_64) format |
Date: |
Thu, 9 Feb 2012 00:35:11 +0000 |
User-agent: |
KMail/1.13.7 (Linux/3.1.0-1-amd64; KDE/4.6.5; x86_64; ; ) |
> > starting your own toy kernel is a fun thing to do and there are many
> > tutorials out there on how to do it. Unfortunately when one wants to
> > write a kernel in 64bit it becomes much harder because one can't
> > compile 64bit code as elf32 image and converting a elf64 image to
> > elf32 format is a major hassle and looses debug information and symbols.
So just have two versions of your image:
- The elf64 image that has debug info, symbols, etc. Point gdb at this.
- An elf32 image that you give to the bootloader (in this case kvm)
Generating the latter from the former is a trivial objcopy invocation.
The bootloader variant only needs enough information to get the loadable
sections into memory. We don't care about non-resident clutter like debug
info or symbols. Anything that cares about those will be using the full elf64
image.
This is all standard practice. I don't think I've never actually used a
system where the image loaded by the target is the same file as the one that
comes out of the linker and is used by the debugger.
> Yes, this is why I asked about support in other software. If each
> bootloader implements a different custom method then it will be a pain
> to run your binary on real hardware in the future. It's worth at
> least checking their source first - maybe there is already a similar
> code path that we can be compatible with, hence making life easier for
> developers who want to play with 64-bit payloads in multiboot
> executables.
The whole idea of entering a 64-bit image in 32-bit mode seems distinctly
sketchy. Surely it'd make more sense to define a 64-bit multiboot variant and
do the job properly.
Paul
- [Qemu-devel] Support for multiboot images in elf64 (EM_X86_64) format, Goswin von Brederlow, 2012/02/04
- Re: [Qemu-devel] Support for multiboot images in elf64 (EM_X86_64) format, Stefan Hajnoczi, 2012/02/06
- Re: [Qemu-devel] Support for multiboot images in elf64 (EM_X86_64) format, Goswin von Brederlow, 2012/02/08
- Re: [Qemu-devel] Support for multiboot images in elf64 (EM_X86_64) format, Kevin Wolf, 2012/02/08
- Re: [Qemu-devel] Support for multiboot images in elf64 (EM_X86_64) format, Stefan Hajnoczi, 2012/02/08
- Re: [Qemu-devel] Support for multiboot images in elf64 (EM_X86_64) format,
Paul Brook <=
- Re: [Qemu-devel] Support for multiboot images in elf64 (EM_X86_64) format, Goswin von Brederlow, 2012/02/09
- Re: [Qemu-devel] Support for multiboot images in elf64 (EM_X86_64) format, Paul Brook, 2012/02/09
- Re: [Qemu-devel] Support for multiboot images in elf64 (EM_X86_64) format, Goswin von Brederlow, 2012/02/09
- Re: [Qemu-devel] Support for multiboot images in elf64 (EM_X86_64) format, Paul Brook, 2012/02/09